During the next year we will assess the interrelation of major nutrients (e.g., calories, protein, carbohydrates, total and saturated fats, oleic and linoleic acids, and cholesterol) with various steroid and polypeptide hormones possibly related to the risk of developing breast cancer. The effect of dietary fat on steroid and polypeptide hormone profiles (as assayed from urine and blood samples) will continue to be evaluated in two studies. First, ten Seventh-day Adventist (SDA) vegetarian and ten SDA non-vegetarian premenopausal women who have recently been studied on three separate occasions will have their three-day dietary records analyzed (Objective 1). Plasma and urine levels of estrone, estradiol-17Beta, estriol and plasma prolactin will be determined by radioimmunoassay. Interrelationships between plasma and urinary hormones and dietary nutrient intakes will be evaluated. Similar hormone profiles will be separately assessed in a controlled human metabolic diet study lasting 10 weeks (Objective 2). This study will involve eight SDA lacto-ovovegetarian premenopausal women and will evaluate the effects of feeding low fat (25% of calories) and high fat (45%) diets. Prolactin secretion tests will be conducted during the metabolic dietary study as a means of assessing the hypothalamic-pituitary response to low and high fat diets. The two studies will permit an evaluation of the influence of various dietary nutrients and fat levels on steroid and polypeptide hormone profiles during several menstrual cycles. The findings of this study are potentially of major importance; from these data an insight should be gained into interrelationships among diet, hormones, and their possible roles in the etiology of breast cancer.